1. Technical Field
The present invention relates to a tuner device for a radio receiver, and more in particular, to a tuner device suitable for a vehicle digital radio receiver for receiving a radio wave transmitted from a satellite (hereinafter, referred to as satellite wave) or an radio wave transmitted from an earth station (hereinafter, referred to as terrestrial wave) so as to listen to digital radio broadcasting.
2. Related Art
Recently, digital radio receivers receiving a satellite wave or a terrestrial wave so as to listen to digital radio broadcasting have been developed and put into practical use in the United States. In general, the digital radio receivers can be mounted in a mobile object such as a vehicle to receive the radio wave in the frequency band of about 2.3 GHz for listening to the radio broadcasting. That is, the digital radio receivers are radio receivers for receiving the mobile broadcasting. Since the frequency of the reception radio wave is about 2.3 GHz, the reception wavelength (resonance wavelength) λ is about 128.3 mm. The terrestrial wave is retransmitted as a linearly-polarized wave by receiving the satellite wave in an earth station and slightly shifting the frequency of the received satellite wave. That is, the satellite wave is a circularly-polarized wave, whereas the terrestrial wave is the linearly-polarized wave.
Thus, in such digital radio broadcasting, since the radio wave having the frequency band of about 2.3 GHz is used, it is necessary to install an antenna for receiving the radio wave outdoors. Accordingly, when the digital radio receiver is mounted on a vehicle, the antenna of the digital radio receiver need be disposed on the roof of the vehicle. Such a vehicle antenna and receiver body (head unit) disposed in the interior of the vehicle are electrically connected to each other via a cable. The head unit serves as an external device. The head unit is also called a user set.
Such a system for receiving the satellite wave or the terrestrial wave includes an antenna unit (antenna device) and a tuner unit (satellite radio tuner). The antenna unit (antenna device) receives the satellite wave or the terrestrial wave and then outputs the received signal at a high frequency. The tuner unit (satellite radio tuner) demodulates the received signal and then outputs a sound signal.
In general, electronic component constituting such a tuner are mounted on a printed circuit board (tuner substrate) and housed in a metallic case (shield case) used commonly as a shield (for example, see Patent Document 1). Patent Document 1 discloses an example in which a tuner device (tuner pack) is fixed perpendicular to a main substrate. The connector pins mounted on the tuner pack are inserted and then soldered to holes formed in a main substrate. In addition, fixation pieces formed in the shield case are introduced into holes formed in the main substrate, and then soldered to the earth patterns formed around the holes.
A configuration of an exemplary satellite digital radio receiver will be described with reference to FIG. 8. The satellite digital radio receiver includes an antenna 101, a tuner unit 102, a signal demodulator 103, a channel demodulator 104, a sound decoder 105, a data decoder 106, a control unit 107, and an operating unit 108 (for example, see Patent Document 2).
Further, a tuner case has been proposed which can be used for both vertical fixation (vertical arrangement) and face-down fixation (horizontal arrangement) (for example, see Patent Document 3). Patent Document 3 discloses that fixation legs are provided to the side surface and the bottom surface (bottom surface) of the tuner case and only a single case, thereby enabling both vertical fixation and face-down fixation by the use of a single case.
Patent Document 1: JP-A-6-209268
Patent Document 2: JP-A-2002-344335
Patent Document 3: JP-A-2001-136464
As disclosed in Patent Document 1, the tuner module is formed of a printed circuit board mounting the circuit component, and a metallic case for housing the printed circuit board so as to shield the circuit component thereon. In the tuner module disclosed in Patent Document 1, the metallic case (shield case) is made of a solderable material. Hence, the tuner module can be vertically disposed in the main substrate by inserting the connector pin and the fixation pieces to the holes (square hole) of the main substrate. Thus, by vertically disposing the tuner module on the main surface of the main substrate, the user's need of utilizing effectively any available space can be satisfied.
On the other hand, in order to form with high precision or without machine finishing, the metallic case (shield case) is sometimes made as an aluminum die-cast body. However, since aluminum is an unsolderable material, it is difficult to vertically install the tuner module on the main surface of the main substrate. As a result, the user's need of utilizing effectively the surplus space can not be satisfied.
In any case, when the metallic case (shield case) is formed of an unsolderable material such as aluminum, in order to vertically install the tuner module, it is necessary to hold the tuner module using any holding means.
Patent Document 3 only proposes a tuner case that can be used as a vertical fixation (vertical arrangement) as well as a face-down fixation (horizontal arrangement), but does not disclose any materials for use in the metallic case (shield case).
In addition, an RF input portion connected to an end portion of a coaxial cable for transmitting a high frequency (RF) signal received at an antenna device. In this case, stress on a soldered portion, originating from vibration or tensile cannot be readily reduced by simply soldering between the end portion of the coaxial cable and the RF input portion.
Further, the tuner device is sometimes packed at the time of shipment while the end portion of the coaxial cable is connected to the RF input portion. However, it is difficult to compactly pack the tuner device due to an obstacle of the coaxial cable. In addition, the tuner device is sometimes soldered by the user on the main surface of the main substrate using a solder deep bath, with the end portion of the coaxial cable connected to the RF input portion. In this case, the coaxial cable is apt to be dropped into the solder deep bath by mistake.